1. Field of the Invention
The present invention relates to liquid ejection heads that perform recording on a target surface by ejecting liquid in a form of droplets, and in particular to inkjet recording heads that each include a nozzle plate having nozzles through which ink is ejected and a substrate having energy generating elements.
2. Description of the Related Art
A so-called side-shooter recording head includes a substrate, a nozzle plate having nozzles provided therein in correspondence with energy generating elements provided on the substrate, and channels provided therebetween.
Referring to FIG. 7, an exemplary known technique is disclosed in U.S. Pat. No. 6,799,831, in which a row of nozzles provided along each of supply ports is surrounded by a groove for preventing separation of a nozzle plate from a substrate. A recording head H1101 shown in FIG. 7 has a plurality of nozzles 6 and grooves 3 each surrounding a group of the nozzles 6. Since the coefficients of linear expansion of the substrate, the nozzle plate, and a tank case (a substrate holding member) that holds the substrate are different, if heat is generated during printing or if the environment in which the recording head is stored changes, the interfaces between the components are subjected to stresses. Such stresses include a stress due to hardening shrinkage of an adhesive or a sealant for bonding or sealing the tank case and the substrate. Moreover, the substrate itself of the recording head is easy to be deformed because of the supply ports provided therein.
Such stresses are particularly influential on regions where the nozzle plate ends (ends of the nozzle plate), i.e., ends of channel walls defining the channels, and the grooves provided around the nozzles and the channels. Therefore, separation of the nozzle plate from the substrate may occur. To avoid the separation, the grooves 3 according to the technique disclosed in U.S. Pat. No. 6,799,831 have a sawtooth shape, thereby relaxing stresses applied to the joint between the substrate and the nozzle plate.
However, it has been found that the sawtooth-shaped groove may trigger another problem. In general, when a printer is activated, foreign substances such as paper lint and dust are generated from a recording medium. If printing is performed with foreign substances caught on the surface of the nozzle plate, characteristics including wettability of the surface of the nozzle plate may change. In some cases, such foreign substances may cover some of the nozzles, resulting in defective print such as deflection of the ejecting direction and no ejection of ink.
To solve such a problem, some known printers having recording heads each include a mechanism that removes foreign substances that are caught around nozzles so as to perform stable ejection. In general, such a mechanism includes a recovery pump and a wiping member. FIG. 9 shows an exemplary recovery pumping mechanism provided for a recording head 1000. Referring to FIG. 9, the recovery pumping mechanism, which includes a capping member 13 that caps a recording head, pumps foreign substances caught on the surface of the nozzle plate and a little amount of ink from the recording head. Subsequently, ink remaining on the surface of the nozzle plate after the pumping by the recovery pumping mechanism is removed by a wiping member 12.
Recently, however, there has been a demand for realizing a low-cost printer body by excluding such a recovery pumping mechanism but without deteriorating performance. If the recovery pumping mechanism is excluded, the recovery operation only includes wiping of the surface of the nozzle plate with the wiping member. Referring to FIG. 8, if a foreign substance 8 such as paper lint is caught by the groove 3 provided in the nozzle plate because the groove 3 has a sawtooth shape, it is difficult in some cases to remove foreign substances only by wiping. If foreign substances remain caught around the nozzles 6, characteristics, including wettability, of the surface of the nozzle plate may change and some of the nozzles may be clogged, resulting in defective print such as deflection of the ejecting direction and no ejection of ink.